Monday, January 07, 2013

Assault Weapons Part 1: Battle Rifle to Assault Rifle

This is part one of a series on "assault weapons", a topic likely to be in the news a great deal as the new congress tackles the possibility of new gun control measures. The term "assault weapon" is itself a frequently disputed one, having come in to currency with the "assault weapons" ban of 1994 (which expired to little fanfare in 2004.) It is based on the term "assault rifle" though the weapons legally defined as "assault weapons" by the ban were not technically assault rifles. Thus I am going to start out by examining the development of the "assault rifle" as a piece of military technology.

Looking back to the early days of our country, muzzle loading black powder muskets and rifles hurled large pieces of lead at comparatively low velocities (under 1000 feet per second). Muskets in the Revolutionary War shot .75 caliber musket balls. Caliber refers to the diameter of the bullet and it's normally a fractional number of inches. Thus, the musket balls of the Revolutionary War were three quarters of an inch in diameter. By the Civil War, musket balls were replaced by bullet-shaped .58 caliber "minie-balls". Although they were smaller in diameter, they were longer, so the actual mass was similar: 500-600 grains which translates to 1.1 to 1.4 ounces. (If you want a way to think about this, a quarter weights .2 ounces or 87 grains, so a Revolutionary or Civil War bullet weighed about as much as a stack of six quarters.)

Trapdoor Springfield

After the Civil War, the army adopted cartridge-based rifles. First the black powder .45 caliber "trapdoor" Springfield, a single shot cartridge rifle whose breech flipped open to load. Then, in 1892, the five shot .30 caliber Krag-Jørgensen bolt action rifle, which was the first US military rifle to use smokeless powder, shooting the .30-40 Government cartridge.

M1903 Springfield Bolt Action

Although each of these developments in military technology featured a lighter bullet with a smaller diameter, each also fired the bullet at higher velocity. Energy is calculated as mass times velocity squared times a constant of 1/2. By this calculation, the .30-06 bullets which World War I and II US Soldiers used packed more than twice as much energy as a Civil War era minie-ball, despite weighting only 150 grains (a bit less than the weight of two quarters.)

Improvements in weapons technology had consistently made rifles both faster to shoot and accurate to longer distances. Muzzle loading muskets and later rifles, from the time of the Revolutionary War to the Civil War could be fired at a rate of three shots per minute by trained soldiers, but while the smoothbore muskets of the Revolution were accurate, at best, to a hundred yards, the Civil War era rifles could be accurate out to 300 yards or more. This drastic increase in the accurate range of small arms was one of the factors that significantly changed battle tactics from those of the Napoleonic era. Several decades before, a mass infantry charge such as Picket's famous charge at Gettysburg could have been a decisive means of victory. With the longer range rifled muskets of the Civil War, it led to mass slaughter.

While muzzle loading technology had imposed a fairly strict limit on the rate of fire that infantry soldiers could deliver, the introduction of cartridge rifles allowed significant increases . While a Civil War era rifled musket could only be fired three time a minute even by soldiers well trained in speed drill, the single shot, cartridge loading "trapdoor" Springfield could get off ten shots a minute. The bolt action, five shot M1903 Springfields used during World War One allowed a soldier to get off fifteen aimed shots a minute.

Technological improvements had continued to increase the accuracy of battle rifles as well. By the first world war, the rifles carried by all of the major combatants were no longer limited by the technical specifications of the rifle but by the ability of their users. All of the battle rifles used in the Great War fired bullets of roughly .30 caliber from high powered cartridges and could hit a man-sized target at distances of 800-1000 yards. The issue was: Although the rifles were technically capable of hitting a target at such extreme distances, none but the most skilled snipers had either the eyesight or the steadiness to hit targets at that distance. Indeed, the majority of battlefield fire was exchanged at distances of less than 300 yards.

In the 1920s, the US military began to search for a new standard service rifle, which was to be the first semi-automatic service rifle. A number of designs were tested, and the one eventually selected was the M1 Garand, named after its designer John Garand. Throughout much of its development, the military planned to have the M1 chambered for a lighter cartridge in .276 caliber, however at a late date it had the rifle re-engineered to shoot the same .30-06 as the M1903 Springfield because so much .30-06 ammunition was already on hand. The M1 was adopted as the standard US infantry rifle in 1936, and the US was thus the only major power in World War II whose primary battle rifle was not a bolt action. However, the M1 shot the same kind of high powered .30 caliber cartridge which all of the other battle rifles of the war shot.

US Service Rifles: Two M1903 Sprinfields, an M1 Garant, an M1 Carbine,
an M14 and an M16 (Click to See Larger)

It was in World War II that the need for a lighter gun suitable for rapid fire became increasingly obvious. For most of the war this was achieved through specialization. Most infantry soldiers carried full size battle rifles and a smaller number were issued sub machine guns -- lighter weapons which could shoot in fully automatic (firing continuously as long as the trigger was held down) or burst mode (firing bursts of 3-5 shots every time the trigger was pulled.) To make then easy to handle (and allow them to carry more rounds) sub machine guns shot smaller, pistol cartridges rather than a full size rifle cartridge and was thus suitable only for short range.

Tom Hanks holding a Thompson
Sub Machine Gun in Saving Private Ryan

Military technologists were convinced that a cross between a full sized battle rifle and a sub machine gun was needed. Such a gun would shoot a rifle cartridge, but a lighter one which would not have as much recoil as a high power .30 round. It should also be capable of shooting in burst or fully automatic mode as well as semi-automatic mode (one shot for each pull of the trigger.)

Germany produced what is often regarded as the first true "assault rifle" near the end of World War II, the Sturmgewehr 44. It shot a shortened .30 caliber bullet with a lighter charge of powder behind it, making the recoil lighter and the ammunition cheaper to produce and lighter to carry, and it could shoot either in semi-auto or full-auto mode. By late 1943, however, the tide was already turning against Germany and its manufacturing capacity was waning. Only half a million were ever produced (compared to over 14 million of their full size K98 Mauser bolt action battle rifle.) However, it provided the inspiration for Mikhail Kalashnikov's development of the AK-47 in Russia after the war. The AK-47 also used a light .30 caliber cartridge and selective fire (the ability to fire either semi-auto or full-auto.) The design became the standard Russian infantry rifle in 1949 and went on to become perhaps the most widely produced rifle design in history.

Sturmgewehr 44

AK-47

The 5.56x45mm round shot by the M16 (left)
next to the 7.62x51mm shot by the M14.

The United States was comparatively late to the game in adopting an assault rifle for its armed forces. After World War II the US sought to improve on the M1 Garand and in 1959 adopted the M14. The M14 did have selective fire and accepted a large detachable magazine. (The Garand had a unique loading mechanism: it's magazine was fixed but clips of eight shots were loaded in from the top. Those eight shots could then be fired as fast as the shooter could pull the trigger. After the last shot, the rifle ejected the metal clip out the top and the bolt locked open. The shooter then loaded a new clip in from the top and released the bolt to load the next cartridge.)

However, the M14 still fired a full size .30 cartridge, the 7.62×51mm NATO which fired a bullet of the same size as the .30-06 at the same speed. The rifle had many fans and continues to be used to this day by US soldiers and marines who are designated marksmen, but the 7.62×51mm NATO proved too high powered a cartridge to be practically shot in burst or full auto mode, and the rifle itself was heavy. As a result, the US Army adopted the M16 for jungle combat in 1963 and in 1969 made the M16 the standard service rifle. The M16, made with an aluminum receiver and a plastic stock, was five inches shorter and three pounds lighter than the M14 and it shot a much smaller cartridge, the 5.56×45mm NATO, with a .22 caliber bullet weighting about a third as much as the .30 caliber bullet of the 7.62×51mm NATO.

Because the bullet is so light and travels at such high velocity, it is extremely accurate even at long distances. However, due to its light weight it packs only half as much energy as full size .30 caliber rounds. This makes the M16 much more comfortable to fire, especially rapidly, which is the purpose of the "assault rifle" concept, however troops have in some conditions complained that it lacks "stopping power" and in Iraq and Afghanistan many units have a designated marksman with an M14 for situations in which a heavier weapon is needed. For the same reason, many hunters shun the civilian version of the round (the .223 Remington), believing that it is too small to humanely kill deer and other full size game. The round is often found, however, in the "modern sporting rifles" which are similar appearance to military designs. For the recreational shooter, the light rounds fired by military assault rifles are often preferred because they have fairly light recoil, are highly accurate at the 100-200 yard distances found at most rifle ranges, and because ammunition is far less expensive than the larger high powered hunting rounds.

Military technology has continued to develop, but all standard service rifles since the 1960's have been variations on the assault rifle concept. The standard US service rifle is the M4 Carbine, a slightly modernized version of the M16 design.

M4 Carbine

More recent assault rifles adopted by other nations all have the basic features of selective fire and smaller rifle cartridges. More modern innovations generally relate either to compactness (a number place the action in the stock, behind the trigger, allowing for a shorter overall length of the rifle even while keeping the same length barrel) or modularity.

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